U.S. patent application number 15/962738 was filed with the patent office on 2018-08-23 for methods of identifying and locating tissue abnormalities in a biological tissue.
The applicant listed for this patent is EMTensor GmbH. Invention is credited to Serguei Y SEMENOV.
Application Number | 20180235486 15/962738 |
Document ID | / |
Family ID | 51530390 |
Filed Date | 2018-08-23 |
United States Patent
Application |
20180235486 |
Kind Code |
A1 |
SEMENOV; Serguei Y |
August 23, 2018 |
METHODS OF IDENTIFYING AND LOCATING TISSUE ABNORMALITIES IN A
BIOLOGICAL TISSUE
Abstract
A method of identifying and locating tissue abnormalities in a
biological tissue includes irradiating an electromagnetic signal,
via a probe defining a transmitting probe, in the vicinity of a
biological tissue. The irradiated electromagnetic signal is
received at a probe, defining a receiving probe, after the signal
is scattered/reflected by the biological tissue. Blood flow
information pertaining to the biological tissue is provided. Based
on the received irradiated electromagnetic signal and the blood
flow information, tissue properties of the biological tissue are
reconstructed. A tracking unit determines the position of at least
one of the transmitting probe and the receiving probe while the
step of receiving is being carried out, the at least one probe
defining a tracked probe. The reconstructed tissue properties are
correlated with the determined probe position so that tissue
abnormalities can be identified and spatially located.
Inventors: |
SEMENOV; Serguei Y; (Vienna,
AT) |
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Applicant: |
Name |
City |
State |
Country |
Type |
EMTensor GmbH |
Vienna |
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AT |
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Family ID: |
51530390 |
Appl. No.: |
15/962738 |
Filed: |
April 25, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14788042 |
Jun 30, 2015 |
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15962738 |
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13894401 |
May 14, 2013 |
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14788042 |
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61802339 |
Mar 15, 2013 |
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13894401 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 5/0507 20130101;
A61B 2560/0431 20130101; A61B 5/7278 20130101; A61B 5/7282
20130101; A61B 2576/02 20130101; A61B 5/0295 20130101; A61B 5/7246
20130101; A61B 5/053 20130101; A61B 5/004 20130101; A61B 5/0456
20130101; A61B 5/0265 20130101; A61B 5/7289 20130101 |
International
Class: |
A61B 5/0265 20060101
A61B005/0265; A61B 5/00 20060101 A61B005/00; A61B 5/0295 20060101
A61B005/0295; A61B 5/053 20060101 A61B005/053; A61B 5/05 20060101
A61B005/05 |
Claims
1. A method of identifying and locating tissue abnormalities in a
biological tissue, comprising: irradiating an electromagnetic
signal, via a probe, in the vicinity of a biological tissue, the
probe defining a transmitting probe; at a probe, receiving the
irradiated electromagnetic signal after the signal is
scattered/reflected by the biological tissue, the probe defining a
receiving probe; providing blood flow information pertaining to the
biological tissue; based on the received irradiated electromagnetic
signal and the blood flow information, reconstructing tissue
properties of the biological tissue; determining, via a tracking
unit, the position of at least one of the transmitting probe and
the receiving probe while the step of receiving is being carried
out, the at least one probe defining a tracked probe; and
correlating the reconstructed tissue properties with the determined
probe position so that tissue abnormalities can be identified and
spatially located.
2. The method of claim 1, wherein the step of determining includes
determining the position of the tracked probe at multiple points in
time.
3. The method of claim 1, further comprising a step of correlating
the determined position of the tracked probe to known information
about the position and contours of the biological tissue.
4. The method of claim 3, wherein the known information about the
position and contours of the biological tissue is determined by
carrying out a surfacing process, prior to the step of receiving
the irradiated electromagnetic signal, wherein the position of the
tracked probe, in at least two dimensions, is repeatedly determined
as the tracked probe is placed in different locations against the
surface of the biological tissue, thereby developing a digital map
of the surface of the biological tissue, and wherein the known
information about the position and contours of the biological
tissue includes the digital map.
5. The method of claim 3, further comprising a step of mapping the
status of the tissue.
6. The method of claim 5, wherein the step of mapping the status of
the tissue utilizes matching data from a database, wherein the
matching data in the database is based on previous experiments with
animals and clinical studies with patients.
7. The method of claim 5, further comprising a step of imaging the
tissue.
8. The method of claim 1, wherein the transmitting probe is the
same probe as the receiving probe.
9. The method of claim 1, wherein the transmitting probe is a
different probe from the receiving probe, and wherein the tracked
probe includes both the transmitting probe and the receiving probe,
all while the step of receiving is being carried out.
10. The method of claim 1, further comprising a preliminary step of
determining whether the tracked probe is in the vicinity of the
biological tissue, and further comprising a step of providing an
indication, via the tracked probe, as to whether the tracked probe
is determined to be in the vicinity of the biological tissue.
11. The method of claim 10, wherein the step of determining whether
the tracked probe is in the vicinity of the biological tissue is
based at least in part upon knowledge of electromagnetic signal
differences in biological tissue, air, and a gel.
12. The method of claim 1, wherein the step of determining the
position of the probe includes determining the position of at least
three sensors disposed and spatially separated within the probe
that receives the irradiated electromagnetic signal, and wherein
the step of determining the position of the probe includes
determining the position of the probe in three dimensions.
13. The method of claim 1, wherein the blood flow information is
provided at least partly on the basis of a step of synchronizing
the received electromagnetic signal with a signal representing a
blood circulation cycle of the biological tissue and further on a
step, after the synchronizing step, of processing the synchronized
signals using coherent averaging.
14. The method of claim 1, further comprising steps of: analyzing
the received signal based at least upon the provided blood flow
information and upon knowledge of electromagnetic signal
differences in normal, suspicious, and abnormal tissue; and using a
dielectric properties reconstruction algorithm, reconstructing
dielectric properties of the biological tissue based at least upon
results of the analyzing step and upon blood flow information.
15. The method of claim 14, wherein the step of reconstructing
tissue properties is based at least in part upon results of the
step of reconstructing dielectric properties and upon blood flow
information.
16. The method of claim 14, wherein the step of analyzing the
received signal includes a preliminary step of obtaining the
knowledge of electromagnetic signal differences in normal,
suspicious, and abnormal tissue during clinical procedures, and
wherein the step of obtaining the knowledge of electromagnetic
signal differences in normal, suspicious, and abnormal tissue
during clinical procedures includes correlating information about a
particular electromagnetic signal with information from one or more
tissue pathological study.
17. The method of claim 1, wherein the irradiated electromagnetic
signal is a first electromagnetic signal, wherein the received
electromagnetic signal is a second electromagnetic signal and
wherein the method further comprises a step of processing the first
and second electromagnetic signals using a Doppler sub-block.
18. The method of claim 17, wherein the blood flow information is
provided at least partly on the basis of a step of synchronizing an
output of the Doppler sub-block with a signal representing a blood
circulation cycle of the biological tissue, and wherein the step of
providing the blood flow information includes providing at least
one of: (i) information about a volume of the blood flow, (ii)
information about a velocity of the blood flow, and (iii)
information about a direction of the blood flow.
19. The method of claim 1, wherein the step of reconstructing
tissue properties of the biological tissue includes reconstructing
at least one of: cellular volume fraction (VFcell), (ii)
intracellular conductivity (.sigma.intracell), and (iii)
extracellular conductivity (.sigma.extracell).
20. The method of claim 1, wherein the step of correlating the
reconstructed tissue properties with the determined probe position
includes conducting visualization/imaging and matching analysis,
and wherein dielectric property information based on at least one
of: (i) frequency, and (ii) time, is an input to the step of
conducting visualization/imaging and matching analysis.
21. The method of claim 20, wherein at least one of: (i) cellular
volume fraction (VFcell), (ii) intracellular conductivity
(.sigma.intracell), and (iii) extracellular conductivity
(.sigma.extracell), is an input to the step of conducting
visualization/imaging and matching analysis.
22. The method of claim 20, wherein the step of conducting
visualization/imaging and matching analysis is based at least in
part upon results of a step of analyzing the received signal based
at least upon the provided blood flow information and upon
knowledge of electromagnetic signal differences in normal,
suspicious, and abnormal tissue.
23. The method of claim 20, wherein the step of conducting
visualization/imaging and matching analysis is based at least in
part upon results of the step of providing the blood flow
information, and wherein the step of providing the blood flow
information includes providing at least one of: information about a
volume of the blood flow, (ii) information about a velocity of the
blood flow, and (iii) information about a direction of the blood
flow.
24. The method of claim 23, wherein the blood flow information is
provided at least partly on the basis of a step of synchronizing
the received electromagnetic signal with a signal representing a
blood circulation cycle of the biological tissue.
25. A method of identifying and locating tissue abnormalities in a
biological tissue, comprising: irradiating an electromagnetic
signal, via a probe, in the vicinity of a biological tissue, the
probe defining a transmitting probe; at a probe, receiving the
irradiated electromagnetic signal after the signal is
scattered/reflected by the biological tissue, the probe defining a
receiving probe; providing blood flow information pertaining to the
biological tissue; based on the received irradiated electromagnetic
signal and the blood flow information, reconstructing tissue
properties of the biological tissue; determining, via a tracking
unit, the position of at least one of the transmitting probe and
the receiving probe while the step of receiving is being carried
out, the at least one probe defining a tracked probe; correlating
the reconstructed tissue properties with the determined probe
position so that tissue abnormalities can be identified and
spatially located; and providing an indication of whether the
tissue at the determined probe position is normal or abnormal.
26. The method of claim 25, wherein the steps of irradiating,
receiving, providing blood flow information, reconstructing,
determining, and correlating are carried out repeatedly, and
wherein the step of providing an indication is carried out in the
form of producing an image of the tissue showing areas of normal
tissue distinguished from areas of abnormal tissue.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present invention is a U.S. divisional patent
application of, and claims priority under 35 U.S.C. .sctn. 120 to,
U.S. nonprovisional patent application Ser. No. 14/788,042, filed
Jun. 30, 2015, which '042 application published as U.S. Patent
Application Publication no. 2015/034272 on Dec. 3, 2015, and which
'042 application is a U.S. continuation patent application of, and
claims priority under 35 U.S.C. .sctn. 120 to, U.S. nonprovisional
patent application Ser. No. 13/894,401, filed May 14, 2013, which
'401 application published as U.S. Patent Application Publication
no. 2014/0275944 on Sep. 18, 2014, and which '401 application is a
U.S. nonprovisional patent application of, and claims priority
under 35 U.S.C. .sctn. 119(e) to, U.S. provisional patent
application Ser. No. 61/802,339, filed Mar. 15, 2013. Each of the
foregoing patent applications and patent application publications
is expressly incorporated by reference herein in its entirety.
COPYRIGHT STATEMENT
[0002] All of the material in this patent document is subject to
copyright protection under the copyright laws of the United States
and other countries. The copyright owner has no objection to the
facsimile reproduction by anyone of the patent document or the
patent disclosure, as it appears in official governmental records
but, otherwise, all other copyright rights whatsoever are
reserved.
BACKGROUND OF THE PRESENT INVENTION
Field of the Present Invention
[0003] The present invention relates generally to electromagnetic
field-based bio-sensing and bio-imaging, and in particular, to a
handheld probe-based electromagnetic field technology that allows
clinicians to assess functional and pathological conditions of
biological tissue on-line at the point of care
Background
[0004] The successful management of a fractured bone involves an
understanding of the two major components of any limb segment.
These two components are the osseous or boney element and the soft
tissue elements. Soft tissue elements are the skin, muscle, nerve
and vessels while osseous element includes only the bone. The
diagnosis and evaluation of the boney component is obvious to the
treating physician by radiographic studies. The accurate assessment
of the soft tissue component of the injured limb segment remains a
major deficiency in management of fractures. To date several
methods; such as laser Doppler and transcutaneous oxygen tensions
have been attempted but they have been no better than clinical
judgment. None of these methods have correlated with outcome.
Consequently there is an important need to develop a simple
effective method of assessing soft tissue viability.
[0005] It is important to understand soft tissue injury, as this
component is often the determinant of the final outcome. The soft
tissues provide the blood supply for the bone to heal, provide the
coverage for the bone and the muscles, nerves and vessels provide
for a functional outcome following injury. With the advent of
higher energy trauma, more and more significant soft tissue
disruption is being seen. The clinical problem exists with closed
or open fractures as there is no method at the present to
objectively evaluate soft tissue damage prior to surgical
treatment. The surgical approach causes further damage to the soft
tissues leading to necrosis, wound slough and infection.
Consequently, surgeons require a method to accurately and
objectively establish soft tissue viability so as to minimize the
complication rate. In addition, associated injuries to the muscle
such as a compartment syndrome and arterial disruption require soft
tissue viability assessment to plan an appropriate management. A
compartment syndrome occurs after an injury to an extremity when
the obligatory muscle swelling becomes excessive. If the involved
muscle is contained in an enclosed fascial space, this swelling
will compromise arteriolar muscle blood flow leading to what has
been called "a heart attack" of skeletal muscle. The issue of early
diagnosis of compartment syndrome is very important, and is not
limited to the management of fractures. The swollen limb without
fracture is commonly seen and should be urgently assessed by
orthopedic specialists. Undiagnosed compartment syndrome leads to
muscle necrosis, contracture and irreversible neurological
deficits. Extensive irreversible muscle damage can eventually
result in sepsis or amputation. The incidence of complications is
related to the speed in diagnosis and timing of fasciotomy. For
this reason, delay of diagnosis and lack of aggressive surgical
intervention has resulted in a high rate and amount of indemnity
payment. In most patients, clinical examination is the most
sensitive method of early diagnosis but in obtunded, head injured,
or critically ill patients physical signs and symptoms are
unreliable. Objective data is required in these situations and
these measurements must be accurate and reproducible for diagnosis.
Currently pressure measurements are the best means of determining
need for fasciotomy but clinicians are unable to reach a consensus
as to the critical pressure threshold. In addition, these tests are
invasive, technique dependent, subjective and position
sensitive.
[0006] Clinicians are always looking for simple non-invasive
painless tests which provide the accurate clinical data necessary
to make a rapid diagnosis. As to the monitoring of soft tissue
viability in assessment of crush injuries, free muscle flap
viability, arterial injury and reperfusion, at present there is not
a consistent reliable instrument that is safe and non invasive. In
this aspect, the concept of current invention is very appealing to
the orthopaedic trauma surgeons as a method of non-invasive tissue
viability assessment and monitoring. This technique would provide
the surgeon with a measure of the soft tissue viability associated
with a fracture. This would allow the treating surgeon to time
surgical intervention appropriately, to avoid major disastrous
complications and to be able to prognosticate the long-term
functional outcome for patients. The invented technology combined
with plain radiology in the acute emergency situation would provide
the treating surgeon with a complete assessment of both components
of any given injury. This would enhance drastically the ability of
surgeons to provide quality and effective care for extremity
injuries.
[0007] Various technologies making use of electromagnetic field
phenomena in diagnosing, imaging, and treating various medical
conditions. One of these technologies, electromagnetic tomography
(EMT), is a relatively recent imaging modality with great potential
for biomedical applications, including a non-invasive assessment of
functional and pathological conditions of biological tissues. Using
EMT, biological tissues are differentiated and, consequentially,
can be imaged based on the differences in tissue dielectric
properties. The dependence of tissue dielectric properties from its
various functional and pathological conditions, such as blood and
oxygen contents, ischemia and infarction malignancies has been
demonstrated. Two-dimensional (2D), three-dimensional (3D) and even
"four-dimensional" (4D) EMT systems and methods of image
reconstruction have been developed over the last decade or more.
Feasibility of the technology for various biomedical applications
has been demonstrated, for example, for cardiac imaging and
extremities imaging. Various patents and patent applications have
discussed these technologies, including U.S. Pat. Nos. 5,715,819,
6,026,173, 6,332,087, 6,490,471, and 7,239,731, and U.S. patent
application Ser. No. 13/173,078 (filed Jun. 30, 2011 and published
on Jan. 12, 2012 as U.S. Patent Application Publication No.
2012/0010493 A1) and U.S. patent application Ser. No. 61/801,965
(filed Mar. 15, 2013) (a copy of the latter of which is attached
hereto as Appendix A). The entirety of each of these patents and
patent applications (and any publication of same) is incorporated
herein by reference at least so far as such incorporation is
consistent with the disclosure set forth herein.
[0008] Unfortunately, traditional EMT technologies, while producing
very useful results, have required equipment that is physically
cumbersome and difficult to use. This can be true both for the
technician, diagnostician, or the like as well as the person or
animal who is being studied. With regard to latter, the discomfort
caused by the imaging chamber can also be significant. The size and
weight of the equipment also makes it very difficult to use the
equipment in the place where it is assembled; disassembling and
moving the equipment is not very feasible. Finally, the use of
arrays of antenna and other equipment creates significant
complexity and cost. Thus, a need exists for technology that
produces similar results but in a cheaper, more convenient, and
more comfortable physical form. In particular a need exists for a
more convenient, probe-based, hand-held technology that allows
clinicians to assess functional and pathological conditions of
biological tissue on-line at the point of care.
SUMMARY OF THE PRESENT INVENTION
[0009] Broadly defined, the present invention according to one
aspect is a handheld electromagnetic field-based bio-sensing and
bio-imaging system for use with a biological object, including: a
handheld control unit; a handheld probe, connected to the control
unit, that may be manipulated around a biological object while the
probe irradiates an electromagnetic field, generated by the control
unit, into the biological object and while the probe receives the
irradiated electromagnetic field after being scattered and/or
reflected by the biological object; and a tracking unit that tracks
the position of the handheld probe.
[0010] In a feature of this aspect, the handheld probe is a first
probe, and wherein the system further includes a second probe,
connected to the control unit, that also irradiates an
electromagnetic field. In a further feature, the second probe may
manipulated around the biological object as it irradiates the
electromagnetic field; the received electromagnetic field is
analyzed in conjunction with other data to create an image, in at
least two dimensions, of the biological object around which the
probe is manipulated; the second probe is stationary relative to
the biological object and to the first probe; and/or the second
probe also receives an irradiated electromagnetic field, and
wherein the second received electromagnetic field is also analyzed
in conjunction with other data to create the image, in at least two
dimensions, of the biological object around which the probes are
manipulated.
[0011] In another feature of this aspect, the probe includes a
waveguide. In further features, the waveguide is a ceramic
waveguide; and/or the waveguide is a rectangular waveguide.
[0012] In another feature of this aspect, the probe includes a
plurality of sensors whose positions are tracked by the tracking
unit. In a further feature, the probe includes at least three
sensors whose positions are tracked by the tracking unit.
[0013] In another feature of this aspect, an electromagnetic signal
is generated by a Vector Network Analyzer and travels through a
cable to a probe placed on the biological object where the
electromagnetic signal is used to generate the electromagnetic
field that is irradiated into the biological object.
[0014] In another feature of this aspect, the biological object is
a human tissue. In a further feature, the received electromagnetic
field is analyzed in conjunction with other data to create an
image, in at least two dimensions, of the biological object around
which the probe is manipulated.
[0015] In another feature of this aspect, the tracking unit may be
external to the handheld control unit.
[0016] In another feature of this aspect, the tracking unit may be
internal to the handheld control unit.
[0017] In another feature of this aspect, an electromagnetic signal
is generated by a Vector Network Analyzer and travels through a
cable to a first probe where the electromagnetic signal is used to
generate the electromagnetic field that is irradiated into the
biological object, and wherein the irradiated electromagnetic field
is scattered and/or reflected by the biological object and received
by a second probe. In further features, the scattered and/or
reflected electromagnetic field is captured by an antenna device
within the second probe and analyzed by the handheld control unit
to determine functional and/or pathological conditions of the
biological object; and/or the scattered and/or reflected
electromagnetic field above is captured by an antenna device within
the second probe and analyzed by the handheld control unit to
determine if there is blood flow reduction.
[0018] In another feature of this aspect, the received
electromagnetic field is analyzed in conjunction with other data to
create an image, in at least two dimensions, of the biological
object around which the probe is manipulated.
[0019] Broadly defined, the present invention according to another
aspect is a method of assessing a functional and/or pathological
condition of a biological tissue, including: generating, via a
handheld control unit, an electromagnetic signal, the
electromagnetic signal defining a first signal; communicating at
least a portion of the first signal from the handheld control unit
to a handheld probe via a wired connection; at the handheld probe,
irradiating the first signal into the biological tissue; receiving
the irradiated signal after the irradiated signal is
scattered/reflected by the biological tissue, the received
irradiated signal defining a second signal; combining at least a
portion of the first signal with at least a portion of the second
signal; and processing the combined portions of the first and
second signals to assess the normalcy of the biological tissue.
[0020] In a feature of this aspect, the step of processing the
combined first and second signals to assess the normalcy of the
biological tissue is carried out at the handheld control unit.
[0021] In another feature of this aspect, the step of combining at
least a portion of the first signal with at least a portion of the
second signal is carried out by a Doppler sub-block. In further
features, the step of combining at least a portion of the first
signal with at least a portion of the second signal is carried out
by a directional coupler within the Doppler sub-block; the
directional coupler is a dual direction coupler; the directional
coupler includes a first port, a second port, and a third port such
that the first signal is received at the first port, at least a
portion of the first signal is provided from the first port to, and
output from, the second port, the second signal is received at the
second port after being scattered/reflected by the biological
tissue, and a portion of the second signal that is received at the
second port is coupled with the portion of the first signal and
output from the third port; and/or the directional coupler further
includes a fourth port such that the portion of the first signal is
a first portion, and a second portion of the first signal is output
from the fourth port.
[0022] In another feature of this aspect, the method further
includes a step of determining, via a tracking unit, the position
of the handheld probe while the handheld probe is irradiating the
first signal into the biological tissue.
[0023] In another feature of this aspect, the step of receiving the
irradiated signal after the irradiated signal is
scattered/reflected by the biological tissue is carried out at an
antenna in the handheld probe.
[0024] In another feature of this aspect, the handheld probe is a
first handheld probe, and wherein the step of receiving the
irradiated signal after the irradiated signal is
scattered/reflected by the biological tissue is carried out at a
second handheld probe. In a further feature, the method further
includes a step of determining, via a tracking unit, the position
of the second handheld probe while the second handheld probe is
receiving the irradiated signal after the irradiated signal is
scattered/reflected by the biological tissue.
[0025] In another feature of this aspect, the step of combining at
least a portion of the first signal with at least a portion of the
second signal includes generating, via a directional coupler, a
forward coupling path and a reverse coupling path. In further
features, the step of combining at least a portion of the first
signal with at least a portion of the second signal includes
amplifying each of the forward coupling path and the reverse
coupling path; the forward coupling path is connected to a first
power splitter and the reverse coupling path is connected to a
second power splitter; a first output of the first power splitter
is connected to a first mixer, wherein a second output of the first
power splitter is connected to a second mixer, wherein a first
output of the second power splitter is connected to the first
mixer, wherein a second output of the second power splitter is
connected to the second mixer; an output of the first mixer is
connected to a low pass filter, and an output of the second mixer
is connected to a low pass filter; an output of the first mixer is
connected to an analog-to-digital converter and an output of the
second mixer is connected to an analog-to-digital converter; and/or
processing the combined portions of the first and second signals to
assess the normalcy of the biological tissue includes processing an
output of the analog-to-digital converter.
[0026] Broadly defined, the present invention according to another
aspect is a method of assessing status of a biological tissue,
including: irradiating an electromagnetic signal, via a probe, into
a biological tissue; receiving the irradiated electromagnetic
signal after the signal is scattered/reflected by the biological
tissue; providing blood flow information pertaining to the
biological tissue; analyzing the received signal based at least
upon the provided blood flow information and upon knowledge of
electromagnetic signal differences in normal, suspicious, and
abnormal tissue; using a dielectric properties reconstruction
algorithm, reconstructing dielectric properties of the biological
tissue based at least upon results of the analyzing step and upon
blood flow information; and using a tissue properties
reconstruction algorithm, reconstructing tissue properties of the
biological tissue based at least in part upon results of the
reconstructing step and upon blood flow information.
[0027] In a feature of this aspect, the method further includes a
preliminary step of determining whether the probe is in the
vicinity of the biological tissue. In further features, the method
further includes a step of providing an indication, via the probe,
as to whether the probe is determined to be in the vicinity of the
biological tissue; the step of determining whether the probe is in
the vicinity of the biological tissue is based at least in part
upon knowledge of electromagnetic signal differences in biological
tissue, air, and a gel; the method further includes a preliminary
step of obtaining the knowledge of electromagnetic signal
differences in biological tissue, air, and a gel via one or more
physical/biophysical experiment; and/or the step of determining
whether the probe is in the vicinity of the biological tissue
includes determining whether the probe is in physical contact with
the biological tissue.
[0028] In another feature of this aspect, receiving the irradiated
electromagnetic signal includes receiving the irradiated
electromagnetic signal at a probe. In further features, the probe
via which the electromagnetic signal is irradiated is the same
probe as the probe at which the irradiated electromagnetic signal
is received; the probe via which the electromagnetic signal is
irradiated is a different probe from the probe at which the
irradiated electromagnetic signal is received; the method further
includes a step of determining whether the probe at which the
irradiated electromagnetic signal is received is in the vicinity of
the biological tissue; the step of determining whether the probe at
which the irradiated electromagnetic signal is received is in the
vicinity of the biological tissue includes determining whether such
probe is in physical contact with the biological tissue; the method
further includes a step of determining, via a tracking unit, the
position of the probe that receives the irradiated electromagnetic
signal while the step of receiving is being carried out; the step
of determining includes determining the position of a sensor
disposed in the probe that receives the irradiated electromagnetic
signal; the step of determining includes determining the position
of at least three sensors disposed within the probe that receives
the irradiated electromagnetic signal; the at least three sensors
are spatially separated within the probe; the step of determining
includes determining the position of the probe in three dimensions;
the step of determining includes determining the position of the
probe at multiple points in time; the method further includes a
step of correlating the determined position of the probe to known
information about the position and contours of the biological
tissue; the method further includes a surfacing process, carried
out prior to the step of receiving the irradiated electromagnetic
signal, wherein the position of the probe, in at least two
dimensions, is repeatedly determined as the probe is placed in
different locations against the surface of the biological tissue,
thereby developing a digital map of the surface of the biological
tissue that is subsequently used in the correlating step; the
reconstructed tissue properties are combined with the results of
the correlating step to produce information regarding the status of
the tissue relative to the geometry of the biological tissue; the
method further includes a step of mapping the status of the tissue;
the step of mapping the status of the tissue utilizes matching data
from a database; the matching data in the database is based on
previous experiments with animals and clinical studies with
patients; and/or the method further includes a step of imaging the
tissue based on the mapping step.
[0029] In another feature of this aspect, the blood flow
information is provided at least partly on the basis of a step of
synchronizing the received electromagnetic signal with a signal
representing a blood circulation cycle of the biological tissue. In
further features, the blood flow information is provided at least
partly on the basis of a step, after the synchronizing step, of
processing the synchronized signals using coherent averaging;
and/or the step of providing the blood flow information includes
providing blood volume information.
[0030] In another feature of this aspect, the irradiated
electromagnetic signal is a first electromagnetic signal, wherein
the received electromagnetic signal is a second electromagnetic
signal and wherein the method further comprises a step of
processing the first and second electromagnetic signals using a
Doppler sub-block. In further features, the blood flow information
is provided at least partly on the basis of a step of synchronizing
an output of the Doppler sub-block with a signal representing a
blood circulation cycle of the biological tissue; and/or the step
of providing the blood flow information includes providing blood
volume information.
[0031] In another feature of this aspect, the step of analyzing the
received signal includes a preliminary step of obtaining the
knowledge of electromagnetic signal differences in normal,
suspicious, and abnormal tissue during clinical procedures. In a
further feature, the step of obtaining the knowledge of
electromagnetic signal differences in normal, suspicious, and
abnormal tissue during clinical procedures includes correlating
information about a particular electromagnetic signal with
information from one or more tissue pathological study.
[0032] In another feature of this aspect, the step of
reconstructing tissue properties of the biological tissue includes
reconstructing cellular volume fraction (VF.sub.cell).
[0033] In another feature of this aspect, the step of
reconstructing tissue properties of the biological tissue includes
reconstructing intracellular conductivity
(.sigma..sub.intracell).
[0034] In another feature of this aspect, the step of
reconstructing tissue properties of the biological tissue includes
reconstructing extracellular conductivity
(.sigma..sub.extracell).
[0035] In another feature of this aspect, the method further
includes a step, after the step of reconstructing tissue properties
of the biological tissue, of conducting visualization, imaging and
matching analysis. In further features, the step of conducting
visualization, imaging and matching analysis is based at least in
part upon results of the step of reconstructing dielectric
properties of the biological tissue; dielectric property
information based on frequency is an input to the step of
conducting visualization, imaging and matching analysis; dielectric
property information based on time is an input to the step of
conducting visualization, imaging and matching analysis; the step
of conducting visualization, imaging and matching analysis is based
at least in part upon results of the step of reconstructing tissue
properties of the biological tissue; cellular volume fraction
(VF.sub.cell) is an input to the step of conducting visualization,
imaging and matching analysis; intracellular conductivity
(.sigma..sub.intracell) is an input to the step of conducting
visualization, imaging and matching analysis; extracellular
conductivity (.sigma..sub.extracell) is an input to the step of
conducting visualization, imaging and matching analysis; the step
of conducting visualization, imaging and matching analysis is based
at least in part upon results of the step of analyzing the received
signal; the step of conducting visualization, imaging and matching
analysis is based at least in part upon results of the step of
providing the blood flow information; the step of providing the
blood flow information includes providing blood volume information;
the step of providing the blood flow information includes providing
blood velocity information; the step of providing the blood flow
information includes providing blood direction information; and/or
the blood flow information is provided at least partly on the basis
of a step of synchronizing the received electromagnetic signal with
a signal representing a blood circulation cycle of the biological
tissue.
[0036] Broadly defined, the present invention according to another
aspect is a method of imaging a biological tissue for identifying
and locating tissue abnormalities, including: irradiating an
electromagnetic signal, via a probe, in the vicinity of a
biological tissue, the probe defining a transmitting probe; at a
probe, receiving the irradiated electromagnetic signal after the
signal is scattered/reflected by the biological tissue, the probe
defining a receiving probe; providing blood flow information
pertaining to the biological tissue; using a tissue properties
reconstruction algorithm and blood flow information, reconstructing
tissue properties of the biological tissue; determining, via a
tracking unit, the position of at least one of the transmitting
probe and the receiving probe while the step of receiving is being
carried out, the at least one probe defining a tracked probe; and
correlating the reconstructed tissue properties with the determined
probe position so that tissue abnormalities can be identified and
spatially located.
[0037] In a feature of this aspect, the transmitting probe is the
same probe as the receiving probe.
[0038] In another feature of this aspect, the transmitting probe is
a different probe from the receiving probe. In a further feature,
the tracked probe includes both the transmitting probe and the
receiving probe, all while the step of receiving is being carried
out.
[0039] In another feature of this aspect, the method further
includes a preliminary step of determining whether the tracked
probe is in the vicinity of the biological tissue. In further
features, the method further includes a step of providing an
indication, via the tracked probe, as to whether the tracked probe
is determined to be in the vicinity of the biological tissue; the
step of determining whether the tracked probe is in the vicinity of
the biological tissue is based at least in part upon knowledge of
electromagnetic signal differences in biological tissue, air, and a
gel; the method further includes a preliminary step of obtaining
the knowledge of electromagnetic signal differences in biological
tissue, air, and a gel via one or more physical/biophysical
experiment; and/or the step of determining whether the tracked
probe is in the vicinity of the biological tissue includes
determining whether the tracked probe is in physical contact with
the biological tissue.
[0040] In another feature of this aspect, the step of determining
includes determining the position of a sensor disposed in the
tracked probe. In further features, the step of determining
includes determining the position of at least three sensors
disposed within the tracked probe; and/or the at least three
sensors are spatially separated within the tracked probe.
[0041] In another feature of this aspect, the step of determining
includes determining the position of the tracked probe in three
dimensions.
[0042] In another feature of this aspect, the step of determining
includes determining the position of the tracked probe at multiple
points in time.
[0043] In another feature of this aspect, the method further
includes a step of correlating the determined position of the
tracked probe to known information about the position and contours
of the biological tissue. In further features, the method further
includes a surfacing process, carried out prior to the step of
receiving the irradiated electromagnetic signal, wherein the
position of the tracked probe, in at least two dimensions, is
repeatedly determined as the tracked probe is placed in different
locations against the surface of the biological tissue, thereby
developing a digital map of the surface of the biological tissue
that is subsequently used in the step of correlating the determined
position to position and contours of the biological tissue; the
method further includes a step of mapping the status of the tissue;
the step of mapping the status of the tissue utilizes matching data
from a database; the matching data in the database is based on
previous experiments with animals and clinical studies with
patients; and/or the method further includes a step of imaging the
tissue.
[0044] In another feature of this aspect, the blood flow
information is provided at least partly on the basis of a step of
synchronizing the received electromagnetic signal with a signal
representing a blood circulation cycle of the biological tissue. In
further features, the blood flow information is provided at least
partly on the basis of a step, after the synchronizing step, of
processing the synchronized signals using coherent averaging;
and/or the step of providing the blood flow information includes
providing blood volume information.
[0045] In another feature of this aspect, the method further
includes a step of analyzing the received signal based at least
upon the provided blood flow information and upon knowledge of
electromagnetic signal differences in normal, suspicious, and
abnormal tissue. In further features, the method further includes a
step of using a dielectric properties reconstruction algorithm,
reconstructing dielectric properties of the biological tissue based
at least upon results of the analyzing step and upon blood flow
information; the step of reconstructing tissue properties is based
at least in part upon results of the step of reconstructing
dielectric properties and upon blood flow information; the step of
analyzing the received signal includes a preliminary step of
obtaining the knowledge of electromagnetic signal differences in
normal, suspicious, and abnormal tissue during clinical procedures;
and/or the step of obtaining the knowledge of electromagnetic
signal differences in normal, suspicious, and abnormal tissue
during clinical procedures includes correlating information about a
particular electromagnetic signal with information from one or more
tissue pathological study.
[0046] In another feature of this aspect, the irradiated
electromagnetic signal is a first electromagnetic signal, wherein
the received electromagnetic signal is a second electromagnetic
signal and wherein the method further comprises a step of
processing the first and second electromagnetic signals using a
Doppler sub-block. In further features, the blood flow information
is provided at least partly on the basis of a step of synchronizing
an output of the Doppler sub-block with a signal representing a
blood circulation cycle of the biological tissue; the step of
providing the blood flow information includes providing blood
volume information; the step of providing the blood flow
information includes providing blood velocity information; and/or
the step of providing the blood flow information includes providing
blood direction information.
[0047] In another feature of this aspect, the step of
reconstructing tissue properties of the biological tissue includes
reconstructing cellular volume fraction (VF.sub.cell).
[0048] In another feature of this aspect, the step of
reconstructing tissue properties of the biological tissue includes
reconstructing intracellular conductivity
(.sigma..sub.intracell).
[0049] In another feature of this aspect, the step of
reconstructing tissue properties of the biological tissue includes
reconstructing extracellular conductivity
(.sigma..sub.extracell).
[0050] In another feature of this aspect, the step of correlating
the reconstructed tissue properties with the determined probe
position includes conducting visualization/imaging and matching
analysis. In further features, dielectric property information
based on frequency is an input to the step of conducting
visualization/imaging and matching analysis; dielectric property
information based on time is an input to the step of conducting
visualization/imaging and matching analysis; cellular volume
fraction (VF.sub.cell) is an input to the step of conducting
visualization/imaging and matching analysis; intracellular
conductivity .sigma..sub.intracell) is an input to the step of
conducting visualization/imaging and matching analysis;
extracellular conductivity (.sigma..sub.extracell) is an input to
the step of conducting visualization/imaging and matching analysis;
the step of conducting visualization/imaging and matching analysis
is based at least in part upon results of a step of analyzing the
received signal based at least upon the provided blood flow
information and upon knowledge of electromagnetic signal
differences in normal, suspicious, and abnormal tissue; the step of
conducting visualization/imaging and matching analysis is based at
least in part upon results of the step of providing the blood flow
information; the step of providing the blood flow information
includes providing blood volume information; the step of providing
the blood flow information includes providing blood velocity
information; the step of providing the blood flow information
includes providing blood direction information; and/or the blood
flow information is provided at least partly on the basis of a step
of synchronizing the received electromagnetic signal with a signal
representing a blood circulation cycle of the biological
tissue.
[0051] Further areas of applicability of the present invention will
become apparent from the detailed description provided hereinafter.
It should be understood that the detailed description and specific
examples, while indicating the preferred embodiment of the
invention, are intended for purposes of illustration only and are
not intended to limit the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0052] Further features, embodiments, and advantages of the present
invention will become apparent from the following detailed
description with reference to the drawings, wherein:
[0053] FIG. 1 is a block diagram of a handheld electromagnetic
field-based bio-sensing and bio-imaging (EMFBioSI) system in
accordance with a preferred embodiment of the present
invention;
[0054] FIG. 2 is a perspective view of one possible implementation
of the handheld control unit and probe of the system of FIG. 1;
[0055] FIG. 3 is a block diagram of the handheld control unit of
the system of FIG. 1;
[0056] FIG. 4 is a block diagram of the Doppler sub-block used in
the system of FIG. 1;
[0057] FIG. 5 is a perspective view of the probe of FIG. 2, being
placed on a human arm;
[0058] FIG. 6A is a perspective view of the probe of FIG. 2;
[0059] FIG. 6B is an exploded perspective view of the probe of FIG.
2, showing three position tracking sensors and a rectangular
waveguide;
[0060] FIG. 7 is a flow diagram of the operational process of the
EMFBioSI system of FIG. 1 in accordance with one or more preferred
embodiments of the present invention;
[0061] FIG. 8 is a block diagram of an EMFBioSI system containing
an internal tracking unit;
[0062] FIG. 9 is a block diagram of the handheld control unit of
the system in FIG. 13;
[0063] FIG. 10 is a block diagram of an EMFBioSI system in
accordance with another preferred embodiment of the present
invention;
[0064] FIG. 11 is a perspective view of one possible implementation
of the handheld control unit and probes of the system of FIG.
6;
[0065] FIG. 12 is a block diagram of the handheld control unit of
the system of FIG. 10;
[0066] FIG. 13 is a perspective view of the two probes of FIG. 11
being placed on an arm;
[0067] FIG. 14 is a flow diagram of the operational process of the
EMFBioSI system of FIG. 10 in accordance with one or more preferred
embodiments of the present invention;
[0068] FIG. 15 is a perspective view of a probe combination in
accordance with another preferred embodiment of the present
invention;
[0069] FIG. 16 is a perspective view of the probe of FIG. 15, being
placed on a human arm;
[0070] FIG. 17A is a graph showing the changes in amplitude of
electromagnetic signals passed through a swine extremity due to a
reduction in femoral artery blood flow;
[0071] FIG. 17B is a graph showing the changes in phase of
electromagnetic signals passed through a swine extremity due to a
reduction in femoral artery blood flow;
[0072] FIG. 18A is a graph showing the changes in amplitude and
phase of electromagnetic signals passed through a swine extremity
due to elevated compartmental pressure; and
[0073] FIG. 18B is a graph showing the reduction in femoral blood
flow due to elevated compartmental pressure in FIG. 18A.
DETAILED DESCRIPTION
[0074] As a preliminary matter, it will readily be understood by
one having ordinary skill in the relevant art ("Ordinary Artisan")
that the present invention has broad utility and application.
Furthermore, any embodiment discussed and identified as being
"preferred" is considered to be part of a best mode contemplated
for carrying out the present invention. Other embodiments also may
be discussed for additional illustrative purposes in providing a
full and enabling disclosure of the present invention. As should be
understood, any embodiment may incorporate only one or a plurality
of the above-disclosed aspects of the invention and may further
incorporate only one or a plurality of the above-disclosed
features. Moreover, many embodiments, such as adaptations,
variations, modifications, and equivalent arrangements, will be
implicitly disclosed by the embodiments described herein and fall
within the scope of the present invention.
[0075] Accordingly, while the present invention is described herein
in detail in relation to one or more embodiments, it is to be
understood that this disclosure is illustrative and exemplary of
the present invention, and is made merely for the purposes of
providing a full and enabling disclosure of the present invention.
The detailed disclosure herein of one or more embodiments is not
intended, nor is to be construed, to limit the scope of patent
protection afforded the present invention, which scope is to be
defined by the claims and the equivalents thereof. It is not
intended that the scope of patent protection afforded the present
invention be defined by reading into any claim a limitation found
herein that does not explicitly appear in the claim itself.
[0076] Thus, for example, any sequence(s) and/or temporal order of
steps of various processes or methods that are described herein are
illustrative and not restrictive. Accordingly, it should be
understood that, although steps of various processes or methods may
be shown and described as being in a sequence or temporal order,
the steps of any such processes or methods are not limited to being
carried out in any particular sequence or order, absent an
indication otherwise. Indeed, the steps in such processes or
methods generally may be carried out in various different sequences
and orders while still falling within the scope of the present
invention. Accordingly, it is intended that the scope of patent
protection afforded the present invention is to be defined by the
appended claims rather than the description set forth herein.
[0077] Additionally, it is important to note that each term used
herein refers to that which the Ordinary Artisan would understand
such term to mean based on the contextual use of such term herein.
To the extent that the meaning of a term used herein--as understood
by the Ordinary Artisan based on the contextual use of such
term--differs in any way from any particular dictionary definition
of such term, it is intended that the meaning of the term as
understood by the Ordinary Artisan should prevail.
[0078] Regarding applicability of 35 U.S.C. .sctn. 112, 6, no claim
element is intended to be read in accordance with this statutory
provision unless the explicit phrase "means for" or "step for" is
actually used in such claim element, whereupon this statutory
provision is intended to apply in the interpretation of such claim
element.
[0079] Furthermore, it is important to note that, as used herein,
"a" and "an" each generally denotes "at least one," but does not
exclude a plurality unless the contextual use dictates otherwise.
Thus, reference to "a picnic basket having an apple" describes "a
picnic basket having at least one apple" as well as "a picnic
basket having apples." In contrast, reference to "a picnic basket
having a single apple" describes "a picnic basket having only one
apple."
[0080] When used herein to join a list of items, "or" denotes "at
least one of the items," but does not exclude a plurality of items
of the list. Thus, reference to "a picnic basket having cheese or
crackers" describes "a picnic basket having cheese without
crackers," "a picnic basket having crackers without cheese," and "a
picnic basket having both cheese and crackers." Finally, when used
herein to join a list of items, "and" denotes "all of the items of
the list." Thus, reference to "a picnic basket having cheese and
crackers" describes "a picnic basket having cheese, wherein the
picnic basket further has crackers," as well as describes "a picnic
basket having crackers, wherein the picnic basket further has
cheese."
[0081] Referring now to the drawings, in which like numerals
represent like components throughout the several views, the
preferred embodiments of the present invention are next described.
The following description of one or more preferred embodiment(s) is
merely exemplary in nature and is in no way intended to limit the
invention, its application, or uses.
[0082] FIG. 1 is a block diagram of a handheld electromagnetic
field-based bio-sensing and bio-imaging (EMFBioSI) system 110 in
accordance with a preferred embodiment of the present invention.
The system 110 includes a handheld control unit 150, a handheld
probe 164, an external electromagnetic field generator 112, and an
external tracking unit 118. A power supply 122, which may include
an AC/DC converter and one or more batteries, may be provided for
the tracking unit 118.
[0083] FIG. 2 is a perspective view of the handheld control unit
150 and probe 164 of the EMFBioSI system 110, and FIG. 3 is a block
diagram of the control unit 150 of FIG. 1. Notably, unlike prior
art systems, the control unit 150 is not physically cumbersome. The
control unit 150 includes a Doppler sub-block 170, a portable
Vector Network Analyzer (VNA) (for example, Agilent FieldFox 2ports
portable VNA) 156, a tablet computer 162, and a power sub-block
160. The tablet computer 162 provides primary control, including a
primary user interface, to a user. The tablet computer 162 is
communicatively connected to the VNA 156, which generates EM
signals having desired parameters, via a first communication link
169, and is likewise communicatively connected to the Doppler
sub-block 170, which processes received signals after they have
passed through an interrogation region, via a second communication
link 171. The tablet computer 162 is also communicatively connected
to the external tracking unit 118 via a third communication link
173.
[0084] EM signals generated by the VNA 156 pass through the cable
to the probe 164 and interrogate the tissue via irradiation. The EM
signal reflected by or transmitted through the tissue passes back
to VNA 156 through the probe and coaxial cable to the same port (or
a second port, as described later) and the complex reflected or
transmitted EM signal is measured by VNA, for example in form of
amplitude and phase or in form of real and imaginary parts of the
signal. Traditionally, the EM signal irradiated from the first
port, reflected by the sample and measured by the same first port
is called S.sub.11. (Similarly, when a second probe is utilized as
described later, an EM signal irradiated from the second port,
reflected by the sample and measured by the first port is called
S.sub.21.) The overall signal generated by port i and measured in
port j after being affected by the sample is called S.sub.11. All
of this is further discussed elsewhere herein.
[0085] As further described hereinbelow, controlled EM signals
generated by the VNA 156 are also provided to the Doppler sub-block
170 by a fourth communication link 152. The EM signal travels via a
probe connection 168 to the probe 164. In at least some
embodiments, the probe connection 168 utilizes a high quality
coaxial cable 168. As also described below, the probe 164 both
delivers the EM signals and receives them after they pass through
or are reflected by the interrogation region. After being received
by the VNA, they are processed by the Doppler sub-block 170, with
the output being processed by an application on the tablet computer
162.
[0086] FIG. 4 is a block diagram of the Doppler sub-block 170 used
in the system 110. The Doppler sub-block 170 includes a dual
direction coupler 172 having a forward coupling path 174 and a
reverse coupling path 175. The output of the forward coupling path
174 is connected to a first amplifier 176, whose output is
connected to a two-way 90.degree. power splitter 178. The output of
the reverse coupling path 175 is connected to a second amplifier
196 and then a third amplifier 197, whose output is connected to a
two-way 0.degree. power splitter 198. The outputs 179,180,199,200
of the power splitters 178,198 are connected to mixers 181,182
whose outputs 183,184 are connected to low pass filters 185,186.
One device suitable for use as the mixers 181,182 is a
Mini-Circuits ZFM. The output of each low pass filter 185,186 is
connected to a respective amplifier and then to an
analog-to-digital converter (ADC) 210, and the outputs 212,214 of
the ADC 210 are connected to a digital signal processor 220.
[0087] In operation, the EM signal from the VNA 156 is directed to
the probe 164 through a dual direction coupler 172. The same EM
signal passes through a forward coupling path 174, goes through an
amplifier 176, and then passes through a two-way 90.degree. power
splitter 178 to obtain an in-phase signal on one output 179 and a
quadrature phase signal on its other output 180. In at least one
embodiment, the EM signal from the VNA 156 is provided at a level
of 0 dBm (0.001 W), the EM signal passing through the forward
coupling path 174 is with power of -20 dBm (0.01 mW), and the
resulting signal is amplified by 30 dB to +10 dBm (10 mW).
[0088] Meanwhile, the main EM signal from the VNA 156 is directed
to the probe 164 for interrogation of a biological object 163 in
the interrogation region. FIG. 5 is a perspective view of the probe
164, of FIG. 1 used in the EMFBioSI system 110, being placed on a
human arm 163. The EM signal 152 from the VNA 156 is received
directly by the probe 164 through the coaxial cable 168. The probe
164 sends the signal into the tissue of the arm 163. A resulting
signal is reflected and scattered by the tissue of the arm 163 back
to the probe 164, where it is received and sent back to the control
unit 150 via the coaxial cable 168.
[0089] Although only a single probe is utilized in the embodiment
described thus far, it will be appreciated that one or more
additional probes could be utilized. In such an arrangement, a
signal received by one probe could have been transmitted by the
same probe, or by a different probe. Thus, each received signal is
sometimes referred to hereinafter as S.sub.jk, where the index j
refers to the jth port of VNA 156, which has a probe connected to
the port. The jth port generates the original electromagnetic
signal and transmits it to a probe toward the interrogation zone.
The index k refers to the kth port of the VNA 156 which in some
embodiments has a probe connected to the port. The kth port via an
antenna in the probe, receives or collects the reflected/scattered
EM signal. In the EMFBioSI system 110 described thus far, exactly
one probe 164 exists, and therefore j=1, k=1, and the signal
received back at the control unit 150 is designated S.sub.11. Other
embodiments may utilize more than one probe. For example, in an
embodiment described hereinbelow, two probes are utilized. In
various two-probe embodiments, other received signals may, for
example, be designated as S.sub.22, S.sub.21, and S.sub.12.
[0090] Referring again to FIG. 4, part of a reflected EM signal or
field passes through the probe 164 and the cable into the dual
direction coupler 172 where it is directed through the reverse
coupling path 175. The output is passed through two amplifiers
196,197 and then through a two-way 0.degree. power splitter 198 to
obtain an in-phase signal on one output 199 and a quadrature phase
signal on its other output 200. In at least one exemplary
embodiment, the reflected EM signal is received at the dual
direction coupler 172 with power -50 dBm, and is amplified by 60 dB
and then +10 dBm by the two amplifiers 196,197.
[0091] The four signals carried by the respective outputs
179,180,199,200 from the power splitters 178,198 are now combined
for analysis. The in-phase signal on the first output 179 of the
two-way 90.degree. power splitter 178, whose original source was
the VNA 156, and the signal on the first output 199 of the two-way
0.degree. power splitter 198, whose original source was the EM
signal reflected and scattered by the tissue, are sent through a
first mixer 181 (Mini-Circuits ZFM-2000) to produce an in-phase
signal I_out at its output 183. Meanwhile, the quadrature signal on
the second output 180 of the two-way 90.degree. power splitter 178,
whose original source was the VNA 156, and the signal on the second
output 200 of the two-way 0.degree. power splitter 198, whose
original source was the EM signal reflected and scattered by the
tissue, are sent through a second mixer 182 and produce a
quadrature signal Q_out at its output 184. Then I-Out and Q-Out are
each routed through a respective low pass filter 185,186 and into
the ADC 210, and the digitized signals on the ADC outputs 212,214
are provided to the DSP 220 or directly to a computer 162 for
further signal analysis and processing.
[0092] FIG. 6A is a perspective view of the probe 164 of FIG. 1.
FIG. 6B is an exploded perspective view of the probe of FIG. 6A,
showing three position tracking sensors 166 and a waveguide 167. In
at least one embodiment, the waveguide is a rectangular waveguide.
The spatial positions (x(t),y(t),z(t)) of each of the position
tracking sensors 166 over time are tracked by the tracking unit
118. A suitable example of such a unit is the Aurora system by NDI,
available at http://www.ndigital.com/medical. Notably, although the
probe 164 illustrated and described herein includes three sensors
166, it will be appreciated that other embodiments may use more
than three sensors. The three position tracking sensors 166 are
spatially separated within the probe 164 to allow for tracking the
position (x(t),y(t),z(t)) of the probe head 165 during clinical
study in relation to the surface of biological tissue 163. The
position tracking sensors 166 are also used to track the angle at
which the EM signal irradiated from the probe 164 interrogates the
tissue. The information from these sensors 166 is needed in order
to provide two-dimensional tissue surface mapping/imaging, as the
signal location and angle should be known for both surfacing and
proper image reconstruction.
[0093] The core of the probe 164 includes a waveguide 167. In some
embodiments, a waveguide might be rectangular. In some embodiments,
the rectangular waveguide 167 is filled with a matching material
that may be selected or designed such that its dielectric
properties match the dielectric properties of biological tissues
and to minimize the dimensions of the probe 164. In this regard,
the dielectric properties of biological tissues are well known and
tabulated. For example, at 1 GHz they vary from =55+j23 for tissues
with high water content (muscle, skin) to =5+j1.5 for tissues with
low water content (fat, bone). One example of a suitable matching
material is a ceramic with 660 and low attenuation, and one
suitable ceramic waveguide 167 may thus be constructed having
dimensions of, for example, 21.times.7.5.times.53 mm, which result
in corresponding probe dimensions that are within a clinically
acceptable range. Useful dielectric property information may be
found in Gabriel S, Lau R W and Gabriel G 1996, "The dielectric
properties of biological tissues: II. Measurements in the frequency
range 10 Hz to 20 GHz," Phys. Med. Biol. 41 2251-69 ("Gabriel"),
the entirety of which is incorporated herein by reference.
[0094] For rectangular waveguides with A>B (for example, where
A=21 mm and B=7.5 mm), where A and B are the side dimensions of the
waveguide, the lowest critical (cutoff) frequency is in dominant
H.sub.10 mode. The frequency is determined by:
f.sub.1,0=1/2A {square root over (.mu. )} (1)
where:
[0095] A--size [m] of largest side of the waveguide on
cross-section B.times.C;
[0096] f--frequency [Hz];
[0097] .mu.=.mu.*.mu..sub.0 where .mu..sub.0--permeability of
vacuum and .mu.--relative permeability (=1 in our conventional
case);
[0098] = * .sub.0 where .sub.0--permittivity of vacuum and relative
permittivity (=60 in our conventional case). Equation (1) may be
simplified for SI units. Then, using:
c=1/ {square root over (.mu..sub.0 .sub.0)} (2)
where:
[0099] c--speed of light in vacuum=2,9979*10.sup.8 [m/sec]
the following is obtained:
f.sub.1,0=c/2A {square root over (.mu. )} (3)
where ,.mu. are relative complex permittivity and permeability of
the waveguide material. For example, in a conventional case and in
an exemplary rectangular waveguide with dimensions provided above,
and assuming that the real portions of both ,.mu. are higher than
their imaginary parts:
f.sub.1,0=c/2A {square root over (.mu. )}=0.29979/(2*0.021* {square
root over (60)})[GHz]=0.921 [GHZ] (4)
Complete details on the above equations (1)-(4) are provided in J.
D. Jackson "Classical Electrodynamics", 3.sup.rd edition, John
Wiley & Sons, Inc, 1999, the entirety of which is incorporated
herein by reference.
[0100] Because the permeability of the majority of biological
tissue is equal to 1, by using a "special material" with
permittivity within a region of 30-60 and with permeability of more
than 1, it is possible to still maintain a good EM match and to
decrease the size of the probe 164, allowing the preferred
embodiment to contain a multi-head (mutli-waveguide) probe.
Suitable ceramic waveguides may be made using a conventional three
step manufacturing process. In a first step, a ceramic plate (in
our exemplary case, with dimensions 53.times.21.times.7.5 mm with
desired hole) is made. This may be done using a proper furnace or
the like to sinter a powder of so called parent compounds. An
example of a parent compound is a barium titanate
(BaTi.sub.4O.sub.9 or Ba.sub.2Ti.sub.9O.sub.20). The second step is
the metallization of all surface of the ceramic plate except the
one that is an EM irradiation surface and excitation hole. This
might be done by applying a highly conductive (usually silver)
paste and then heating. The third step is to connect the outer
conductor of coaxial cable with one metallized surface and inner
conductor with the opposite metallized surface through an
excitation hole. The increased permeability of an EM waveguide is
achieved at the first step of the manufacturing by mixing a powder
of conventional parent compound (for example, a barium titanate
(BaTi.sub.4O.sub.9 or Ba.sub.2Ti.sub.9O.sub.20)) with a powder of
magnetic materials of high permeability and small losses at
microwave frequencies. Conventional ferrites (for example, NiZn or
MnZn) have shown high permeability at low (kHz) frequencies but
exhibit significant decrease in permeability and increase in losses
at high (MHz-GHz) frequencies. The frequencies of our interest are
near 1 GHz. This frequency region is of great interest for various
industrial applications of materials with high magnetic
permeability, for example wireless communications and data storage.
In our case, potential useful magnetic materials might include 1)
nanocrystaline Fe--Co--Ni--B based material with effective magnetic
permeability of about 500-600 at 1GHz region [4], Co--Fe--Zr--B or
Co--Fe--Si--B; and/or 2) novel hexa-ferrites (with formula
M(Fe.sub.12O.sub.19), where M is usually barium Ba, strontium,
Calcium Ca or Lead Pb) with complex permittivity and permeability
that can vary with composition of materials and frequency.
Technology Algorithms and Work Flow
[0101] FIG. 7 is a flow diagram of the operational process 300 of
the EMFBioSI system 110 of FIG. 1 in accordance with one or more
preferred embodiments of the present invention. As shown therein,
this process 300 utilizes a number of input signals, including
S.sub.11, introduced in FIG. 4; an internal clock 314; the output
of the Doppler sub-block 170, introduced in FIG. 4; sensor signals
318, and an electrocardiography (ECG) or plethysmography signal
116. The process 300 also utilizes additional data and other
information, obtained or derived prior to operation and stored in a
database or elsewhere in the system 110. Such information, which
serves as control data, includes material type information (control
data) 310 pertaining to the how the characteristics of S.sub.11
vary based on whether S.sub.11 passes through tissue, air, or a
gel, and tissue status information (control data) 312 pertaining to
"normal," "suspicious," and "abnormal" characteristics of S.sub.11.
Such material type information or control data 310 may be obtained
via physical/biophysical experiments, while the tissue status
information or control data 312 may be obtained during previous
clinical procedures when a particular EM signal S.sub.11 is
correlated with tissue pathological studies.
[0102] The material type control data 310 is used in a decision
block 316 where it is determined whether the probe 164 is on
biologic tissue 163 or not. In order to facilitate ease of use by
the operator, an indication of whether the probe 164 is properly on
the tissue 163 or not. Such an indication might include a green
light, a beep, or the like. A corresponding indication when the
probe 164 is not on the tissue, such as a red light, a buzzer, or
the like, may also be provided. The material type control data 310
is also provided as an input to a filter 320. Once it is determined
the probe is on tissue 163 and the signal is within a valid range
to pass the filter 320, the signal is ready for complex S.sub.11
signal analysis at block 326.
[0103] This block 326 also requires input from the tissue status
control data 312 and a blood flow analyzer 350. The tissue status
control data, which corresponds to the differences in the value of
S.sub.11 resulting from normal, suspicious, or abnormal tissue, is
stored in a computer database and is compared on-line with a
received EM signal S.sub.11. Correlation and cross-correlation
analysis as well as pattern recognition methods may be used.
[0104] The blood flow analyzer 350 is based on the use of a Doppler
signal that has been processed using R-wave synchronization at
block 340 and coherent averaging at block 342. This is explained as
follows. A signal at Doppler frequency is small and comparable to
noise. At block 342, a coherent averaging process is used to detect
a signal with amplitude, which is comparable or less than the
amplitude of noise. Assume N realizations of similar signals x(t)
with its jth realization in the form:
y.sub.j(t)=x(t)+noise(t)
where x(t) is the signal and noise(t) is random noise, the
averaging over N realizations yields:
y = 1 N j = 1 N y j ( t ) = 1 N Nx ( t ) + 1 N j = 1 N noise ( t )
= x ( t ) + 1 N j = 1 N noise ( t ) ##EQU00001##
[0105] The amplitude of random noise is decreased by a factor of N.
The condition of coherent signals is achieved in at least some
embodiments of the system 110 through synchronization 340,
sometimes referred to herein as R-Wave synchronization (based on
use of the "R" component of the QRS complex seen in a typical
electrocardiogram), of the realizations of the Doppler signal 171
and blood circulation cycles as represented by electrocardiography
(ECG) or plethysmography input signal 116. The received Doppler
signals 171, coherently averaged with respect to the circulation
cycle, are signals x(t) in the above equation example. Coherent
averaging is possible as a result of the synchronization with the
circulatory cycles (R-wave synchronization) that are provided by
independently measured ECG or R-pulses or plethysmography, or by
other means of synchronization with circulatory activity.
[0106] Returning to FIG. 7, the complex S.sub.11 signal analysis is
now performed at block 326 using the input from the tissue status
control data 312, the filter 320, and the blood flow analyzer 350.
By changing the excitation frequency (higher than the dominant
mode), different Transverse Electric (TE) and Transverse Magnetic
(TM) modes will be excited. This also will change the polarization
of the irradiated EM field. By looking at different multi-modal
S.sub.11 it would be possible to assess tissue types and functional
conditions of a particular tissue being studied. Blood flow volume
information, received from "Blood flow analyzer" block 350, is used
in the "Complex S.sub.11 Signal Analysis" 326 to assess the tissue
related changes in S.sub.11. In particular, the frequency shift of
the received Doppler signal 171 is proportional to the
velocity/direction of the arterial blood flow, and the strength (or
amplitude) of the signal is proportional to the volume of the
flowing arterial blood.
[0107] When the complex S.sub.11 signal analysis 326 is completed,
tissue dielectric properties reconstruction is performed at block
330. This reconstruction utilizes the measured EM signal S.sub.11
information and results of the complex S.sub.11 signal analysis
326, output from block 326; information about the volume of blood
received from the blood flow analyzer 350; and a dielectric
properties reconstruction algorithm 332. Blood volume with
tabulated dielectric properties, discussed in the Gabriel
reference, is taken into account when assessing a tissue volume and
its dielectric properties using multi-component dielectric mixture
theory. See Landau L. D. and E. M. Lifshitz, Electrodynamics of
Continuous Media, 2.sup.nd edition, Pergamon Press, Oxford, 1984
("Landau") for details on multi-component dielectric mixture
theory. One example of a suitable dielectric property
reconstruction algorithm is found in Bois KJ, Benally AD and R
Zoughi "Multimode solution for the reflection properties of an
open-ended rectangular waveguide radiating into a dielectric
half-space: the forward and inverse problems," IEEE Trans IM, 1999,
48,6, 1131-1140.
[0108] After the tissue dielectric properties are reconstructed in
block 330, tissue properties, such as cellular volume fraction
(VF.sub.cell), intracellular conductivity (.sigma..sub.intracell),
and extracellular conductivity (.sigma..sub.extracell), are
reconstructed in the dielectric properties analyzer 336. The tissue
property reconstruction carried out by the dielectric properties
analyzer 336 utilizes the bulk dielectric properties of tissue over
frequency and time, obtained from tissue dielectric properties
reconstruction at block 330; information received from the blood
flow analyzer 350 about the volume of blood; and a tissue
properties reconstruction algorithm 338. Again, blood volume with
tabulated dielectric properties is taken into account when
assessing a tissue volume and its dielectric properties using
multi-component dielectric mixture theory. Examples of suitable
tissue properties reconstruction algorithms are found in Semenov S.
Y., Simonova G. I., Starostin A. N., Taran M. G., Souvorov A. E.,
Bulyshev A. E., Svenson R. H., Nazarov A. G., Sizov Y. E., Posukh
V. G., Pavlovsky A., Tatsis G. P., "Modeling of dielectrical
properties of cellular structures in the radiofrequency and
microwave spectrum/Electrically interacting vs non-interacting
cells," Annals of Biomedical Engineering, 2001, 29, 5, 427-435, and
in Semenov S. Y., Svenson R. H., Bulyshev A. E., Souvorov A. E.,
Nazarov A. G., Sizov Y. E., Posukh V. G., Pavlovsky A., Tatsis G.
P., "Microwave spectroscopy of myocardial ischemia and
infarction/2. Biophysical reconstruction," Annals of Biomedical
Engineering, 2000, 28, 1, 55-60. The entirety of each of these
references is incorporated herein by reference.
[0109] During operation of the system 110, it may be necessary or
useful to identify a biological area of interest as a 3D surface in
order to make space-time correlations between the actual position
of the diagnostic probe at a particular time of the procedure and
particular portions of a biological sample under the study. In at
least some embodiments, this is achieved using a "surfacing"
procedure 346 that is conducted during an initial phase of the
clinical study of a biological area of interest. An operator may
move the probe 164 in various ways along an area of assumed
clinical interest while position determinations are conducted. For
example, an operator may first move the probe along the assumed
boundary of an area of clinical interest and second move the probe
along two non-parallel lines inside an area of assumed clinical
interest. Other movement patterns are likewise possible, such as by
making continual lines or by placing the probe at different
points.
[0110] In some situations, such as in the case when movement in an
area of clinical interest is anticipated during a diagnostic
procedure, it may be useful to conduct the surfacing procedure 346
on-line during the diagnostic procedure. In this particular case,
multiple position tracking sensors 166 may be physically attached
directly to biological tissue in a similar manner, for example, the
way that disposable ECG electrodes are conventionally attached to
biological tissue.
[0111] During the surfacing procedure 346, the positions of the
sensors 166 are tracked or determined in three dimensions in the
sensor tracking block 354 and analyzed so that the location and
contours of the surface of biological tissue of clinical interest
are known in two, or preferably three, dimensions and supplied in
digital form into the "probe on tissue tracking" block 352. In this
block 352, the positions of the sensors 166 continue to be tracked
and compared to the known data regarding the surface of the tissue
itself 163 so as to determine the position of the probe 164 on the
tissue 163.
[0112] The operational process 300 culminates at block 370 with
visualization of the position of the probe on the object under
study, imaging of dielectric and other properties (such as those
described below and/or elsewhere herein) of the tissue, and
matching analysis. Here, multi-modal S.sub.11 characteristics (such
as frequency, amplitude, and phase of S.sub.11 signal, and
polarization of E-field for each mode) from the complex S.sub.11
signal analysis at block 326, dielectric property information based
on frequency and time from the tissue dielectric properties
reconstruction at block 330, tissue property information (such as
VF.sub.cell, .sigma..sub.intracell, and .sigma..sub.extracell) from
the dielectric properties analyzer 336, blood flow information such
as volume, velocity, and direction of blood flow from the blood
flow analyzer 350, probe position information from the probe/tissue
position tracker 352, and matching data from a matching database
360 are utilized to provide visualization of the probe position on
the object under study and imaging of dielectric properties of the
tissue 163, and to match characteristics of the EM signal S.sub.11
to tissue properties in order to provide an indication 380 of
tissue status to the operator. The matching database 360 contains
data based on previous experiments with animals and clinical
studies with patients.
[0113] FIG. 8 is a block diagram of an electromagnetic field
bio-sensing and bio-imaging (EMFBioSI) system 210 in accordance
with another preferred embodiment of the present invention. The
system 210 is similar to that of FIG. 1, but has an internal
tracking unit 218.
[0114] FIG. 9 is a block diagram of the handheld control unit 250
of FIG. 8. The block diagram shows the internal tracking unit 218
and its connections to the AC/DC Converters and Battery in the
Power Block 260 and to the Tablet 162.
[0115] FIG. 10 is a block diagram of an electromagnetic field
bio-sensing and bio-imaging (EMFBioSI) system 410 in accordance
with another preferred embodiment of the present invention. The
system 410 is similar to that of FIG. 1, but having two probes
164.
[0116] FIG. 11 is a perspective view of the handheld control unit
450 and two probes 164, 464 of the EMFBioSI system 410, and FIG. 12
is a block diagram of the control unit 450 of FIG. 10. The control
unit 450 is similar to that of FIG. 3, but having a second probe
connection 468 to the second port of the VNA 156 for a second probe
464. In at least some embodiments, the probe connection 468
utilizes a high quality coaxial cable 468. As also described below,
probe 1 164 and probe 2 464 both deliver and collect or receive EM
signals after they pass through the interrogation region. After
being received, they are processed by the Doppler sub-block 170,
with the output being processed by an application on the tablet
computer 162.
[0117] In this EMFBioSI system 410, because there are multiple
probes, it is necessary to use signal indexing as described above.
An EM signal received by one probe could have been transmitted by
the same probe, or by a different probe. Thus, each received signal
is sometimes referred to hereinafter as S.sub.jk, where the index j
refers to the jth port of the VNS that transmits the original
electromagnetic signal from the VNA 156 via a cable and antenna in
the probe 164 toward the interrogation zone, and the index k refers
to the kth port of the VNA 156 that receives the
reflected/scattered signal. In system 410, probe 1 164 irradiates
an EM signal which is scattered by the tissue and then received by
probe 1 164. As in system 110, the signal received by probe 1 is
referred to as S.sub.11. The EM signal irradiated by probe 1 164
may also be received by probe 2 464; if used, this signal is
referred to as S.sub.12. Furthermore, in the system 410 of FIG. 10,
probe 2 464 may also irradiate an EM signal which is scattered by
the tissue and then received by probe 1 164, probe 2 464, or both.
A signal irradiated by probe 2 464 and received by probe 1 164 may
be referred to as S.sub.21; a signal both irradiated and received
by probe 2 464 may be referred to as S.sub.22.
[0118] Referring again to FIG. 12, probe 1 164 receives the
reflected and scattered signals S.sub.11 and S.sub.21 from the arm
tissue and returns a signal to the Doppler Sub-block 170 where
processing continues through just as it does in system 110 and then
the digitized signals on the ADC outputs 212,214 are provided to
the DSP 220 or directly to a computer 162 for further signal
analysis and processing. S.sub.12 is received by the VNA 156 and
passed through a connection to the tablet 162 for further analysis
and processing.
[0119] FIG. 13 is a perspective view of the two probes 164,464 used
in the EMFBioSI system 410, placed on an arm.
[0120] FIG. 14 is a flow diagram of the operational process 500 of
the EMFBioSI system 410 of FIG. 10 in accordance with one or more
preferred embodiments of the present invention and is similar to
the flow diagram of the operational process 300 with the
differences detailed hereinbelow. As shown therein, this process
500 utilizes a number of input signals, including S.sub.jk (where
j=1,2 and k=1,2); an internal clock 314; the output of the Doppler
sub-block 170, introduced in FIG. 4; sensor signals 318, and an
electrocardiography (ECG) or plethysmography signal 116. The
process 500 also utilizes additional data and other information,
obtained or derived prior to operation and stored in a database or
elsewhere in the system 410. Such information, which serves as
control data, includes material type information (control data) 510
pertaining to the how the characteristics of S.sub.jk vary based on
whether S.sub.jk pass through tissue, air, or a gel, and tissue
status information (control data) 512 pertaining to "normal,"
"suspicious," and "abnormal" characteristics of S.sub.jk. Such
material type information or control data 510 may be obtained via
physical/biophysical experiments, while the tissue status
information or control data 512 may be obtained during previous
clinical procedures when a particular EM signal S.sub.jk is
correlated with tissue pathological studies.
[0121] The material type control data 510 is used in a decision
block 516 where it is determined whether both probes 164, 464 are
on biologic tissue 163 or not. In order to facilitate ease of use
by the operator, an indication of whether the probes 164, 464 are
properly on the tissue 163 or not. Such an indication might include
a green light, a beep, or the like. A corresponding indication when
the probes 164, 464 are not on the tissue, such as a red light, a
buzzer, or the like, may also be provided. The material type
control data 510 is also provided as an input to a filter 320. Once
it is determined the probes are on tissue 163 and the signal is
within a valid range to pass the filter 320, the signal is ready
for complex S.sub.jk signal analysis at block 526.
[0122] This block 526 also requires input from the tissue status
control data 512 and a blood flow analyzer 350. The tissue status
control data, which corresponds to the differences in the value of
S.sub.jk resulting from normal, suspicious, or abnormal tissue, is
stored in a computer database and is compared on-line with the
received EM signal S.sub.jk. Correlation and cross-correlation
analysis as well as pattern recognition methods may be used.
[0123] The operational process 500 of the EMFBioSI system 410 of
FIG. 10 receives input from position tracking sensors 166 located
in probe 1 164 and probe 2 464. The information from these sensors
166 is needed in order to provide two dimensional and
three-dimensional tissue surface mapping or tissue imaging, as the
signal location and angle should be known for proper image
reconstruction.
[0124] The operational process 300 culminates with visualization
and imaging and matching analysis at block 370. Here, multi-modal
S.sub.jk characteristics from the complex S.sub.jk signal analysis
at block 326, dielectric property information based on frequency
and time from the tissue dielectric properties reconstruction at
block 330, tissue property information (such as VF.sub.cell,
.sigma..sub.intracell, and .sigma..sub.extracell) from the
dielectric properties analyzer 336, blood flow information such as
volume, velocity, and direction of blood flow from the blood flow
analyzer 350, probe position information from the probe/tissue
position tracker 352, and matching data from a matching database
360 are utilized to provide visualization and imaging of the tissue
163, and to match characteristics of the EM signals S.sub.jk to
tissue properties in order to provide an indication 380 of tissue
status to the operator.
[0125] FIG. 15 is a perspective view of a probe combination in
accordance with another preferred embodiment of the present
invention, and FIG. 16 is a perspective view of the probe of FIG.
15, being placed on a human arm. In this arrangement, a stationary
probe, built into a stable base surface, such as a tabletop, serves
as a second probe, thereby leaving the operator with a free hand
while manipulating the first probe with his or her other hand. The
position of the stationary probe relative to the stable base
surface is thus defined. In at least most other respects, operation
of this system is similar to the two probe implementation described
previously.
Supporting Experimental Results
[0126] FIG. 17A is a graph showing the changes in amplitude of
Electromagnetic signals passed through a swine extremity due to a
reduction in femoral blood flow. FIG. 17B is a graph showing the
changes in phase of Electromagnetic signals passed through a swine
extremity due to a reduction in femoral blood flow. These graphs
show the results of three series of flow reduction (duration 2-3
minutes) through a swine thigh with 10 minute "wash out" periods in
between series. A change in both the amplitude and the phase of
electromagnetic signal was observed immediately after flow
reduction. A linear correlation in amplitude and phase was also
observed (r.sup.2>0.94, p>0.001). The technology demonstrates
very high sensitivity being able to pick up flow reduction
increments of as low as 2 [mL/min]. See Semenov S Y, Kellam J F,
Althausen P, Williams T C, Abubakar A, Bulyshev A and Y Sizov, 2007
Microwave tomography for functional imaging of extremity soft
tissues, Feasibility assessment Phys. Med. Biol., 52, 5705-19.
[0127] FIG. 18A is a graph showing the changes in amplitude and
phase of electromagnetic signals passed through a swine extremity
due to elevated compartmental pressure. FIG. 18B is a graph showing
the decrease in femoral blood flow due to elevated compartmental
pressure in FIG. 18A. Excess of a fluid in the compartment,
depending on the degree of extra-pressure, compromises arterial
blood flow up to the point of a total occlusion, creating tissue
ischemia/infarction. The frequency was 2.5 GHz.
[0128] Based on the foregoing information, it will be readily
understood by those persons skilled in the art that the present
invention is susceptible of broad utility and application. Many
embodiments and adaptations of the present invention other than
those specifically described herein, as well as many variations,
modifications, and equivalent arrangements, will be apparent from
or reasonably suggested by the present invention and the foregoing
descriptions thereof, without departing from the substance or scope
of the present invention.
[0129] Accordingly, while the present invention has been described
herein in detail in relation to one or more preferred embodiments,
it is to be understood that this disclosure is only illustrative
and exemplary of the present invention and is made merely for the
purpose of providing a full and enabling disclosure of the
invention. The foregoing disclosure is not intended to be construed
to limit the present invention or otherwise exclude any such other
embodiments, adaptations, variations, modifications or equivalent
arrangements; the present invention being limited only by the
claims appended hereto and the equivalents thereof.
* * * * *
References